Lubricating structure in piston type compressor

ABSTRACT

A lubricating structure in a piston type compressor has a housing. a rotary shaft, a rotary valve and a shaft seal device. The housing defines a seal chamber, a plurality of cylinder bores and a suction pressure region. The rotary shaft is rotatably supported by the housing and includes a lubricating passage that interconnects the seal chamber and the suction pressure region. The rotary valve is connected to the rotary shaft and includes an introducing passage. The rotary shaft further includes a supply passage that interconnects the introducing passage and the suction pressure region for introducing fluid into the cylinder bores. The shaft seal device is located in the seal chamber and is located between the housing and the rotary shaft for preventing the fluid from leaking along a circumferential surface of the rotary shaft from the housing.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a lubricating structure in a piston type compressor with a shaft seal device that is located between a housing and a rotary shaft to prevent fluid from leaking from the housing along a circumferential surface of the rotary shaft.

[0002] A piston type compressor disclosed in Unexamined Japanese Patent Publication No. 7-63165 employs a rotary valve for introducing refrigerant into a compression chamber defined in a cylinder bore. A double-headed piston in the compressor is reciprocated by the rotation of a swash plate. In this fixed displacement swash plate type compressor, a rotary shaft itself functions as the rotary valve. In comparison to a flapper suction valve that opens and closes a suction port for introducing refrigerant into the compression chamber, a rotary valve that opens and closes the suction port improves volumetric efficiency.

[0003] A shaft seal device is located between a front housing and the rotary shaft and prevents refrigerant in the compressor from leaking to the outside of the compressor along a circumferential surface of the rotary shaft Lubricant oil in the refrigerant lubricates a portion that requires lubrication in the compressor. The shaft seal device needs to be appropriately lubricated by the lubricant oil, otherwise it early degrades so that sealing performance is early deteriorated. In the compressor disclosed in the Unexamined Japanese Patent Publication No. 7-63165, lubrication on the shaft seal device is not sufficiently devised.

SUMMARY OF THE INVENTION

[0004] In accordance with the present invention, a lubricating structure in a piston type compressor has a housing, a rotary shaft, a rotary valve and a shaft seal device. The housing defines a seal chamber, a plurality of cylinder bores and a suction pressure region. The rotary shaft is rotatably supported by the housing and includes a lubricating passage that interconnects the seal chamber and the suction pressure region. The rotary valve is connected to the rotary shaft and includes an introducing passage. The rotary shaft further includes a supply passage that interconnects the introducing passage and the suction pressure region for introducing fluid into the cylinder bores. The shaft seal device is located in the seal chamber and is located between the housing and the rotary shaft for preventing the fluid from leaking along a circumferential surface of the rotary shaft from the housing.

[0005] Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

[0007]FIG. 1A is a longitudinal cross-sectional view of a fixed displacement double-headed piston type compressor according to a first preferred embodiment of the present invention;

[0008]FIG. 1B is a partially cross-sectional view that is taken along the line I-I in FIG. 1A;

[0009]FIG. 2 is a cross-sectional view that is taken along the line II-II in FIG. 1A;

[0010]FIG. 3 is a cross-sectional view that is taken along the line III-III in FIG. 1A;

[0011]FIG. 4 is a longitudinal cross-sectional view of a fixed displacement double-headed piston type compressor according to a second preferred embodiment of the present invention;

[0012]FIG. 5 is a cross-sectional view that is taken along the line IV-IV in FIG. 4;

[0013]FIG. 6 is a cross-sectional view that is taken along the line V-V in FIG. 4;

[0014]FIG. 7A is a longitudinal cross-sectional view of a fixed displacement double-headed piston type compressor according to a third preferred embodiment of the present invention;

[0015]FIG. 7B is a partially cross-sectional view that is taken along the line VI-VI in FIG. 7A;

[0016]FIG. 8 is a cross-sectional view that is taken along the line VII-VII in FIG. 7A;

[0017]FIG. 9A is a longitudinal cross-sectional view of a fixed displacement double-headed piston type compressor according to a fourth preferred embodiment of the present invention;

[0018]FIG. 9B is a partially cross-sectional view that is taken along the line VIII-VIII in FIG. 9A;

[0019]FIG. 10 is a cross-sectional view that is taken along the line IX-IX in FIG. 9A; and

[0020]FIG. 11 is a partially longitudinal cross-sectional view of a fixed displacement double-headed piston type compressor according to a fifth preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] A first preferred embodiment of the present invention will now be described in reference to FIGS. 1A through 3.

[0022] Now referring to FIG. 1A, a diagram illustrates a longitudinal cross-sectional view of a fixed displacement double-headed piston type compressor according to the first preferred embodiment of the present invention. The front side and the rear side of the compressor respectively correspond to the left side and the right side in the drawing. A housing of the compressor includes a pair of front and rear cylinder blocks 11, 12, a front housing 13 and a rear housing 14. The front cylinder block 11 is connected to the rear cylinder block 12. The front housing 13 is connected to the front cylinder block 11. The rear housing 14 is connected to the rear cylinder block 12. The front and rear cylinder blocks 11, 12, the front housing 13 and the rear housing 14 are fastened by a plurality of bolts 10. A discharge chamber 131 is defined in the front housing 13. A discharge chamber 141 and a suction chamber or a suction pressure region 142 are defined in the rear housing 14.

[0023] A valve port plate 15, a valve plate 16 and a retainer plate 17 are interposed between the front cylinder block 11 and the front housing 13. A valve port plate 18, a valve plate 19 and a retainer plate 20 are interposed between the rear cylinder block 12 and the rear housing 14. Discharge ports 151 and 181 are respectively formed in the valve port plates 15 and 18. Discharge valves 161 and 191 are respectively formed in the valve plates 16 and 19 to open and close the respective discharge ports 151 and 181. Retainer 171 and 201 are respectively formed in the retainer plate 17 and 20 to regulate the respective opening degrees of the discharge valves 161 and 191.

[0024] A rotary shaft 21 is rotatably supported by the front and rear cylinder blocks 11, 12 and is inserted into shaft holes 111 and 121 that extend through the front and rear cylinder blocks 11, 12. Namely, the rotary shaft 21 is directly supported by the front and rear cylinder blocks 11, 12 through the respective shaft holes 111 and 121. A lip seal type shaft seal device 22 is interposed between the front housing 13 and the rotary shaft 21 and is located in a seal chamber 132 that is defined in the front housing 13. The shaft seal device 22 prevents refrigerant from leaking along a circumferential surface of the rotary shaft 21 from the housing. The discharge chamber 131 in the front housing 13 is defined around the seal chamber 132.

[0025] A swash plate or a cam 23 is secured to the rotary shaft 21 and is located in a crank chamber or a cam chamber 24 that is defined in the cylinder blocks 11, 12. A thrust bearing 25 is interposed between a rear end surface of the cylinder block 11 and an annular proximal portion 231 of the swash plate 23. A thrust bearing 26 is interposed between a front end surface of the cylinder block 12 and the annular proximal portion 231 of the swash plate 23. The thrust bearings 25 and 26 sandwich the swash plate 23 to regulate a position of the rotary shaft 21 in a direction of an axis 213 of the rotary shaft 21.

[0026] A plurality of front cylinder bores 27 (only one front cylinder bore 27 is shown in the drawing) is formed in the front cylinder block 11. Similarly, a plurality of rear cylinder bores 28 (only one rear cylinder bore 28 is shown in the drawing) is formed in the rear cylinder block 12. Front and rear heads of a double-headed piston 29 are respectively located in the pair of cylinder bores 27, 28. The front and rear cylinder blocks 11, 12 function as a cylinder for the double-headed piston 29. The double-headed piston 29 engages the swash plate 23 through a pair of shoes 30. The swash plate 23 integrally rotates with the rotary shaft 21 and transmits the power of the swash plate 23 to the doubled-headed piston 29 through the shoes 30 so that the double-headed piston 29 reciprocates in the pair of cylinder bores 27, 28. Compression chambers 271 and 281 are defined in the respective cylinder bores 27 and 28 by the double-headed piston 29.

[0027] Sealing portions 112 and 122 are respectively provided at the inner circumferential surfaces of the shaft holes 111 and 121. The sealing portions 112 and 122 are smaller in diameter than the rest of the inner circumferential surfaces of the shaft holes 111 and 121. In other words, the rotary shaft 21 is directly supported by the cylinder blocks 11 and 12 through the respective sealing portions 112 and 122. A supply passage 211 is formed in the rotary shaft 21. The supply passage 211 extends to the rear end of the rotary shaft 21 and communicates with the suction chamber 142 in the rear housing 14. Introducing passages 31 and 32 are formed in the rotary shaft 21 so as to communicate with the supply passage 211.

[0028] A suction passage 33 is formed in the front cylinder block 11 so as to interconnect the cylinder bore 27 and the shaft hole 111. An inlet 331 of the suction passage 33 opens on the sealing portion 112. Similarly, a suction passage 34 is formed in the rear cylinder block 12 so as to interconnect the cylinder bore 28 and the shaft hole 121. An inlet 341 of the suction passage 34 opens on the sealing portion 122. As the rotary shaft 21 rotates, an outlet 311 of the introducing passage 31 intermittently communicates with the inlet 331 of the suction passage 33. Likewise, as the rotary shaft 21 rotates, an outlet 321 of the introducing passage 32 intermittently communicates with the inlet 341 of the suction passage 34.

[0029] When the front cylinder bore 27 is in a suction cycle, that is, when the double-headed piston 29 moves from the left side to the right side in FIG. 1A, the outlet 311 communicates with the inlet 331 of suction passage 33. As a result, refrigerant in the supply passage 211 is introduced Into the compression chamber 271 through the introducing passage 31 and the suction passage 33. When the front cylinder bore 27 is in a discharge cycle, that is, when the double-headed piston 29 moves from the right side to the left side in FIG. 1A, the outlet 311 is disconnected from the inlet 331 of the suction passage 33. As a result, refrigerant in the compression chamber 271 is discharged to the discharge chamber 131 through the discharge port 151 by pushing the discharge valve 161. The refrigerant discharged to the discharge chamber 131 flows out to an external refrigerant circuit, which is not shown in the drawing. The compressor and the external refrigerant circuit constitute a refrigerant circuit, and refrigerant containing lubricant oil flows in the refrigerant circuit.

[0030] Similarly, when the rear cylinder bore 28 is in a suction cycle, that is, when the double-headed piston 29 moves from the right side to the left side in FIG. 1A, the outlet 321 communicates with the inlet 341 of suction passage 34. As a result, refrigerant in the supply passage 211 of the rotary shaft 21 is introduced into the compression chamber 281 through the introducing passage 32 and the suction passage 34. When the rear cylinder bore 28 is in a discharge cycle, that is, when the double-headed piston 29 moves from the left side to the right side in FIG. 1A, the outlet 321 is disconnected from the inlet 341 of the suction passage 34. As a result, refrigerant in the compression chamber 281 is discharged to the discharge chamber 141 through the discharge port 181 by pushing the discharge valve 191. The refrigerant discharged to the discharge chamber 141 flows out to the external refrigerant circuit. The refrigerant flowing out to the external refrigerant circuit returns to the suction chamber 142.

[0031] Rotary valves 35 and 36 are integrated with the rotary shaft 21 and are surrounded by the sealing portions 112 and 122. Communication holes 212 are formed in the circumferential surface of the rotary shaft 21. The communication holes 212 interconnect the supply passage 211 and the seal chamber 132 that accommodates the shaft seal device 22. A lubricating passage 37 includes the communication holes 212 and the supply passage 211 and interconnects the seal chamber 132 and the suction chamber 142. The communication holes 212 communicate with the supply passage 211 at communication openings 214, and the introducing passage 31 of the rotary valve 35 communicates with the supply passage 211 at a communication opening 215. The communication openings 214 are located near the communication opening 215.

[0032] Now referring to FIG. 1B, a diagram illustrates a partially cross-sectional view that is taken along the line I-I in FIG. 1A. The pair of communication holes 212 is formed in a circumferential surface of the rotary shaft 21 and is opposite with each other. The communication holes 212 interconnect the supply passage 211 and the seal chamber 132 so that part of refrigerant containing lubricant oil is introduced into the seal chamber 132 through the communication holes 212. As the rotary shaft 21 rotates, the communication holes 212 orbit around the axis 213 of the rotary shaft 21. The orbital motion of the communication holes 212 prevents the liquid lubricant oil in the seal chamber 132 from returning to the supply passage 211. As a result, the communication holes 212 contribute to lubrication on the shaft seal device 22.

[0033] Now referring to FIG. 2, a diagram illustrates a cross-sectional view that is taken along the line II-II in FIG. 1A. The housing of the compressor is fastened by the five bolts 10. The plurality of front cylinder bores 27 is formed in the front cylinder block 11 and is aligned around the rotary shaft 21. Each of the front cylinder bores 27 accommodates the double-headed piston 29 and communicates with the suction passage 33. Meanwhile, the rotary shaft 21 includes the supply passage 211 and the introducing passage 31 that communicates with the supply passage 211. As the rotary shaft 21 rotates, the introducing passage 31 intermittently communicates with the suction passage 33 for introducing the refrigerant into the front cylinder bore 27. Thus, the rotary shaft 21 functions as the rotary valve 35.

[0034] Now referring to FIG. 3, a diagram illustrates a cross-sectional view that is taken along the line III-III in FIG. 1A. The plurality of rear cylinder bores 28 is formed in the rear cylinder block 12 and is aligned around the rotary shaft 21. Each of the rear cylinder bores 28 accommodates the double-headed piston 29 and communicates with the suction passage 34. Meanwhile, the rotary shaft 21 includes the supply passage 211 and the introducing passage 32 that communicates with the supply passage 211. As the rotary shaft 21 rotates, the introducing passage 32 intermittently communicates with the suction passage 34 for introducing the refrigerant into the rear cylinder bore 28. Thus, the rotary shaft 21 functions as the rotary valve 36.

[0035] According to the first preferred embodiment, the following advantageous effects are obtained.

[0036] (1-1) When the cylinder bores 27, 28 are in a suction cycle, the refrigerant in the suction chamber 142 respectively flows into the compression chambers 271, 281 through the supply passage 211, the introducing passages 31, 32 and the suction passages 33, 34. The part of refrigerant in the suction chamber 142 reaches the seal chamber 132 through the lubricating passage 37 that includes the supply passage 211 and the communication holes 212. The part of lubricant oil in the refrigerant is also introduced into the seal chamber 132 and contributes to lubrication on the shaft seal device 22.

[0037] (1-2) The supply passage 211 extends in the rotary shaft 21 and opens in the suction chamber 142 at one end of the rotary shaft 21 so that the refrigerant in the suction chamber 142 smoothly flows into the supply passage 211 without receiving any centrifugal force due to the rotation of the rotary shaft 21. Meanwhile, the communication holes 212 orbit around the axis 213 of the rotary shaft 21 as the rotary shaft 21 rotates. The orbital motion of the communication holes 212 facilitates the liquid lubricant oil in the supply passage 211 to flow into the seal chamber 132 and prevents the liquid lubricant oil in the seal chamber 132 from returning to the supply passage 211. Namely, the lubricant oil tends to stay in the seal chamber 132. Since the seal chamber 132 tends to keep the lubricant oil in the seal chamber 132, the shaft seal device 22 is sufficiently lubricated.

[0038] (1-3) Since the temperature of the refrigerant is relatively low in the supply passage 211 that communicates with the suction chamber 142, the shaft seal device 22 is cooled down by the refrigerant that is sent from the supply passage 211 to the seal chamber 132. However, if the refrigerant does not flow in and out between the seal chamber 132 and the supply passage 211, the shaft seal device 22 is not efficiently cooled. Generally, the shaft seal device 22 is made of rubber member. When the rubber member heats up, thermal degradation early occurs so that sealing performance is early deteriorated.

[0039] Incidentally, the compression chamber 271 intermittently communicates with the introducing passage 31 as the rotary valve 35 rotates. As a result, pressure regularly raises and lowers in the vicinity of the communication opening 215 between the introducing passage 31 and the supply passage 211. Since the communication openings 214 between the communication holes 212 and the supply passage 211 are located near the communication opening 215, pressure regularly raises and lowers in the vicinity of the communication openings 214. The variation in pressure in the vicinity of the communication openings 214 facilitates the refrigerant to flow in and out between the seal chamber 132 and the supply passage 211. Accordingly, the shaft seal device 22 is efficiently cooled.

[0040] (1-4) The supply passage 211 sends the refrigerant to the introducing passages 31, 32 of the respective rotary valves 35, 36 and constitutes a portion of the lubricating passage 37. A new formed passage for communication is to only form the communication holes 212. Accordingly, It is simple for forming the lubricating passage 37.

[0041] (1-5) The rotary valves 35, 36 are integrated with the rotary shaft 21 in the first preferred embodiment. In comparison to a structure that separately includes rotary valves from a rotary shaft, the number of components is reduced and an assembling process of the compressor is simple in the first preferred embodiment.

[0042] A second preferred embodiment of the present invention will now be described in reference to FIGS. 4 through 6. The same reference numerals denote the substantially identical components to those in the first preferred embodiment.

[0043] Now referring to FIG. 4, a diagram illustrates a longitudinal cross-sectional view of a fixed displacement double-headed piston type compressor according to the second preferred embodiment of the present invention. Rotary valves 39 and 40 are secured to a rotary shaft 38. A pair of thrust bearings 43 and 44 regulates a position of the rotary shaft 38 in a direction of an axis 381 of the rotary shaft 38. Introducing passages 41, 42 are formed in the respective rotary valves 39, 40 and communicate with the crank chamber 24. An outlet 411 of the introducing passage 41 intermittently communicates with the inlet 331 of the suction passage 33 as the rotary valve 39 rotates. Likewise, an outlet 421 of the introducing passage 42 intermittently communicates with the inlet 341 of the suction passage 34 as the rotary valve 40 rotates. A supply passage 382 is formed in the rotary shaft 38. Supply holes 383, 384 are formed in a circumferential surface of the rotary shaft 38 to interconnect the crank chamber 24 and the supply passage 382. Namely, the crank chamber 24 communicates with the suction chamber 142 through the supply holes 383, 384 and the supply passage 382. The refrigerant in the suction chamber 142 is sent to the crank chamber 24 through the supply passage 382 and the supply holes 383, 384. The refrigerant in the crank chamber 24 is introduced into the compression chambers 271, 281 through the respective introducing passages 41, 42 and the suction passages 33, 34 when the cylinder bores 27, 28 are in a suction cycle.

[0044] Communication holes 385 are formed in a circumferential surface of the rotary shaft 38 to interconnect the supply passage 382 and the seal chamber 132 that accommodates the shaft seal device 22. The seal chamber 132 communicates with the suction chamber 142 through a lubricating passage 45 that includes the communication holes 385 and the supply passage 382. The lubricating passage 45 functions as well as the lubricating passage 37 in the first preferred embodiment.

[0045] Now referring to FIG. 5,a diagram illustrates a cross-section view that is taken along the line IV-IV in FIG. 4. The plurality of front cylinder bores 27 is formed in the front cylinder block 11 and is aligned around the rotary shaft 38. Each of the front cylinder bores 27 accommodates the double-headed piston 29 and communicates with the suction passage 33. Meanwhile, the rotary valve 39 includes the introducing passage 41 for introducing the refrigerant into the front cylinder bore 27. As the rotary shaft 38 rotates, the introducing passage 41 intermittently communicates with the suction passage 33.

[0046] Now referring to FIG. 6, a diagram illustrates a cross-sectional view that is taken along the line V-V in FIG. 4. The plurality of rear cylinder bores 28 is formed in the rear cylinder block 12 and is aligned around the rotary shaft 38. Each of the rear cylinder bores 28 accommodates the double-headed piston 29 and communicates with the suction passage 34. Meanwhile, the rotary valve 40 includes the introducing passage 42 for introducing the refrigerant into the rear cylinder bore 28. As the rotary shaft 38 rotates, the introducing passage 42 intermittently communicates with the suction passage 34.

[0047] According to the second preferred embodiment, the advantageous effects mentioned in the paragraph (1-1), (1-2), (1-4) and (1-5) in the first preferred embodiment are obtained.

[0048] A third preferred embodiment of the present invention will now be described in reference to FIGS. 7A through 9. The same reference numerals denote the substantially identical components to those in the first preferred embodiment.

[0049] Now referring to FIG. 7A, a diagram illustrates a longitudinal cross-sectional view of a fixed displacement double-headed piston type compressor according to the third preferred embodiment of the present invention. A lubricating passage 46 extends through the front cylinder block 11, the valve port plate 15, the valve plate 16 and the retainer plate 17. An inlet 461 of the lubricating passage 46 opens in the crank chamber 24, and an outlet 462 of the lubricating passage 46 opens in the seal chamber 132. Namely, the lubricating passage 46 interconnects the seal chamber 132 and the crank chamber 24. The other components are substantially identical To those in the first preferred embodiment.

[0050] The operation of the third preferred embodiment will now be described. When the front cylinder bore 27 is in a suction cycle, the outlet 311 communicates with the inlet 331 of the suction passage 33 so that the refrigerant in the supply passage 211 in the rotary shaft 21 is introduced into the compression chamber 271 through the introducing passage 31 and the suction passage 33. When the front cylinder bore 27 is in a discharge cycle, the outlet 311 is disconnected from the inlet 331 of the suction passage 33 so that the refrigerant in the compression chamber 271 is discharged to the discharge chamber 131 through the discharge port 151 by pushing the discharge valve 161.

[0051] When the rear cylinder bore 28 is in a suction cycle, the outlet 321 communicates with the inlet 341 of the suction passage 34 so that the refrigerant in the supply passage 211 in the rotary shaft 21 is introduced into the compression chamber 281 through the introducing passage 32 and the suction passage 34. When the rear cylinder bore 28 is in a discharge cycle, the outlet 321 is disconnected from the inlet 341 of the suction passage 34 so that the refrigerant in the compression chamber 281 is discharged to the discharge chamber 141 through the discharge port 181 by pushing the discharge valve 191.

[0052] Discharge pressure of the refrigerant in the compression chambers 271, 281 in a discharge cycle is higher than that in the crank chamber 24 that communicates with the suction chamber 142 through the lubricating passage 46, the seal chamber 132 and the supply passage 211. Due to the pressure differential, the refrigerant in the compression chambers 271, 281 in a discharge cycle partially leaks to the crank chamber 24 through gaps between the circumferential surface of the double-headed piston 29 and the inner circumferential surfaces of the cylinder bores 27, 28. The leaked refrigerant causes the pressure in the crank chamber 24 to become slightly higher than that in the supply passage 211 and the suction chamber 142 so that a pressure differential arises between the supply passage 211 and the crank chamber 24. As a result, the refrigerant in the crank chamber 24 flows into the supply passage 211 through the lubricating passage 46, the seal chamber 132 and the communication holes 212.

[0053] Now referring to FIG. 7B, a diagram illustrates a partially cross-sectional view that is taken along the line VI-VI in FIG. 7A. The single lubricating passage 46 is provided for communicating with the seal chamber 132 at the outlet 462

[0054] Now referring to FIG. 8, a diagram illustrates a cross-sectional view that is taken along the line VII-VII in FIG. 7A. The lubricating passage 46 extends through the front cylinder block 11 and is located between the two cylinder bores 27, which are located below the rotary shaft 21 in the drawing.

[0055] According to the third preferred embodiment, the following advantageous effects are obtained.

[0056] (3-1) Since the refrigerant regularly flows through the lubricating passage 46, the seal chamber 132 and the communication holes 212, the lubricant oil in the refrigerant is continuously supplied from the crank chamber 24 to the seal chamber 132 and flows from the seal chamber 132 to the supply passage 211. The part of lubricant oil supplied to the seal chamber 132 through the lubricating passage 46 contributes to lubrication on the shaft seal device 22.

[0057] (3-2) Since the refrigerant flows through the lubricating passage 46, the seal chamber 132 and the communication hole 212, the shaft seal device 22 is cooled. In comparison to the structure without the lubricating passage 46 in the first preferred embodiment, the structure with the lubricating passage 46 that interconnects the seal chamber 132 and the crank chamber 24 further efficiently cools the shaft seal device 22 in the third preferred embodiment.

[0058] Incidentally, as a cross-sectional area of the lubricating passage 46 expands, a temperature in the seal chamber 132 falls. However, as a cross-sectional area of the lubricating passage 46 further expands, a temperature in the seal chamber 132 initiates to rise because the refrigerant in the crank chamber 24 is higher in temperature than that in the suction chamber 142. Therefore, the cross-sectional area of the lubricating passage 46 is determined on experiment or calculation in accordance with the displacement of the compressor. For example, the cross-sectional area of the lubricating passage 46 is determined based on the volume of the crank chamber 24 and pressure differential between the crank chamber 24 and the suction chamber 142.

[0059] (3-3) When the refrigerant in the compression chambers 271, 281 leaks along the circumferential surface of the double-headed piston 29 into the crank chamber 24 that is lower in pressure than the compression chambers 271, 281, the misty lubricant oil in the gaseous refrigerant is separated from the refrigerant so that the lubricant oil is reserved at the bottom of the crank chamber 24. The reserved lubricant oil is scraped up to lubricate the thrust bearings 25, 26 and contact surfaces between the swash plate 23 and the shoes 30. The crank chamber 24 reserving enough lubricant oil is efficient in supplying the lubricant oil. Accordingly, the structure with the lubricating passage 46 that interconnects the seal chamber 132 and the crank chamber 24 is efficient in supplying the lubricant oil for lubricating the shaft seal device 22 in the seal chamber 132.

[0060] (3-4) The compression chamber 271 in the front cylinder bore 27 intermittently communicates with the introducing passage 31 of the rotary valve 35 as the rotary valve 35 rotates. As a result, a vacuum action is generated in the vicinity of the communication opening 215 between the introducing passage 31 and the supply passage 211. The communicating ports 214 between the communication holes 212 and the supply passage 211 are located in the vicinity of the communicating port 215 so that the vacuum action around the communicating port 215 is applied around the communicating ports 214. The application of the vacuum action facilitates the refrigerant to flow from the seal chamber 132 to the supply passage 211 through the communication holes 212. As a result, the application of the vacuum action facilitates the refrigerant to flow from the crank chamber 24 to the supply passage 211 through the lubricating passage 46, the seal chamber 132 and the communication holes 212. The structure with the communication holes 212 located in the vicinity of the introducing passage 31 facilitates the refrigerant to flow through the lubricating passage 46, the seal chamber 132 and the communication holes 212. As a result, the shaft seal device 22 is efficiently lubricated and cooled.

[0061] A fourth embodiment of the present invention will now be described in reference to FIGS. 10A through 11. The same reference numerals denote the substantially identical components to those in the first preferred embodiment.

[0062] Now referring to FIG. 9A, a diagram illustrates a longitudinal cross-sectional view of a fixed displacement double-headed piston type compressor according to the fourth preferred embodiment of the present invention. The bolt 10 is located near the bottom of the compressor and is inserted through a bolt hole 47A that extends through the cylinder blocks 11, 12, the valve port plates 15, 18, the valve plates 16, 19 and the retainer plates 17, 20. A clearance is formed between the circumferential surface of the bolt 10 and the inner circumferential surface of the bolt hole 47A. A through hole 48 is formed in the valve port plate 15, the valve plate 16 and the retainer plate 17 for extending the rotary shaft 21 through. The above described components are substantially identical to those in the first preferred embodiment. In addition, the through hole 48 interconnects the seal chamber 132 and a groove 113 that is recessed in the front end surface of the front cylinder block 11.

[0063] Now referring to FIG. 9B, a diagram illustrates a partially cross-sectional view that is taken along the line VIII-VIII in FIG. 9A. The pair of communication holes 212 is formed in a circumferential surface of the rotary shaft 21 and is opposite with each other. The lubricating passage 37 includes the communication holes 212 and the supply passage 211. Three grooves 113, 114, 115 are recessed in the front end surface of the front cylinder block 11 for communicating with the seal chamber 132.

[0064] Now referring to FIG. 10, a diagram illustrates a cross-sectional view that is taken along the line IX-IX in FIG. 9A. The five bolts 10 are provided for fastening the housing of the compressor. Each of the bolts 10 extends through the respective bolt holes 47A, 47B, 47C, 47D, 47E. The three grooves 113, 114, 115 are recessed in the front end surface of the front cylinder block 11, and each of the grooves 113, 114, 115 interconnects the through hole 48 of FIG. 9A and the respective bolt holes 47A, 47B, 47C, which are located below the rotary shaft 21 In the drawing. A lubricating passage 49A includes the through hole 48, the groove 113 and the bolt hole 47A, and interconnects the crank chamber 24 and the seal chamber 132. Similarly, a lubricating passage 49B includes the through hole 48, the groove 114 and the bolt hole 47B, and a lubricating passage 49C includes the through hole 48, the groove 115 and the bolt hole 47C. The bolt holes 47A, 47B, 47C extend through the front cylinder block 11. The other components are substantially identical to those in the first preferred embodiment.

[0065] Referring back to FIG. 9A, the pressure in the crank chamber 24 is slightly higher than that in the supply passage 211 and the suction chamber 142 due to the leakage of the refrigerant from the compression chambers 271, 281 so that a pressure differential arises between the supply passage 211 and the crank chamber 24. As a result, the refrigerant in the crank chamber 24 flows to the supply passage 211 through the lubricating passages 49A, 49B, 49C, which are shown in FIG. 10, the seal chamber 132 and the communication holes 212.

[0066] According to the fourth preferred embodiment, in addition to the advantageous effects mentioned in the paragraphs (3-1) through (3-4) in the third preferred embodiment, the following advantageous effect is obtained.

[0067] The bolt holes 47A, 47B, 47C, 47D, 47E are parallel with the axis 213 of the rotary shaft 21 and the grooves 113, 114, 115 are recessed in the front end surface of the front cylinder block 11. The bolt holes 47A, 47B 47C, 47D, 47E and the grooves 113, 114, 115 are molded with the front cylinder block 11 at the same time. Accordingly, the lubricating passages 49A, 49B, 49C including the bolt holes 47A, 47B, 47C do not require drilling.

[0068] A fifth preferred embodiment of the present invention will now be described in reference to FIG. 11. The same reference numerals denote the substantially identical components to those in the fourth preferred embodiment.

[0069] Now referring to FIG. 11, a diagram illustrates a partially longitudinal cross-sectional view of a fixed displacement double-headed piston type compressor according to the fifth preferred embodiment of the present invention. A groove 152 is recessed on the rear end of the valve port plate 15 that faces the front end surface of the front cylinder block 11. The groove 152 interconnects the bolt hole 47A and the through hole 48. A lubricating passage 50 includes the through hole 48, the groove 152 and the bolt hole 47A for interconnecting the crank chamber 24 and the seal chamber 132. The other components are substantially identical to those in the fourth preferred embodiment.

[0070] According to the fifth preferred embodiment, the advantageous effects as well as those in the fourth preferred embodiment are obtained.

[0071] The present invention is not limited to the above-described embodiments but may be modified into the following alternative embodiments.

[0072] In alternative embodiments to the above preferred embodiments, a fixed displacement single-headed piston type compressor is employed.

[0073] In alternative embodiments to the above preferred embodiments, a piston type compressor that has a cam in a predetermined shape other than a swash plate is employed.

[0074] In alternative embodiments to the above third preferred embodiment, a plurality of lubricating passages is provided.

[0075] In alternative embodiments to the above third preferred embodiment, the lubricating passage 46 is formed above the rotary shaft 21 in FIG. 8.

[0076] In alternative embodiments to the above fourth preferred embodiment, the number of the lubricating passages is not limited to three. A single lubricating passage is provided or a plurality of lubricating passages other than three is provided.

[0077] In alternative embodiments to the above fourth preferred embodiment, the lubricating passages 49A, 49B, 49C are formed above the rotary shaft 21 in FIG. 10.

[0078] In alternative embodiments to the above fifth preferred embodiment, the groove 152 is recessed in the front end surface of the valve port plate 15 that faces the valve plate 16.

[0079] In alternative embodiments to the above preferred embodiments, a thin plate gasket for preventing gas leakage is interposed between the valve plate 16 and the valve port plate 15, and a slit is formed in the gasket for interconnecting the through hole 48 and the bolt hole.

[0080] Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims. 

What is claimed is:
 1. A lubricating structure in a piston type compressor, comprising: a housing defining a seal chamber, a plurality of cylinder bores and a suction pressure region; a rotary shaft rotatably supported by the housing, the rotary shaft including a lubricating passage that interconnects the seal chamber and the suction pressure region; a rotary valve connected to the rotary shaft, the rotary valve including an introducing passage, the rotary shaft including a supply passage that interconnects the introducing passage and the suction pressure region for introducing the fluid into the cylinder bores; and a shaft seal device located in the seal chamber, the shaft seal device being located between the housing and the rotary shaft for preventing fluid from leaking along a circumferential surface of the rotary shaft from the housing.
 2. The lubricating structure according to claim 1, wherein the rotary valve is integrated with the rotary shaft, the introducing passage being formed in the rotary shaft.
 3. The lubricating structure according to claim 1, wherein the lubricating passage includes the supply passage and a communication hole formed in the circumferential surface of the rotary shaft.
 4. The lubricating structure according to claim 3, wherein the lubricating passage includes a plurality of the communication holes.
 5. The lubricating structure according to claim 3, wherein the communication hole is located near the introducing passage.
 6. A rotary shaft for use in a piston type compressor that has a housing including a seal chamber, a cylinder bore and a suction pressure region, and a shaft seal device located in the seal chamber, the rotary shaft comprising: a supply passage communicating with the suction pressure region; an introducing passage communicating with the supply passage for introducing fluid into the cylinder bore; and a lubricating passage interconnecting the seal chamber and the suction pressure region for introducing the fluid with lubricant in the suction pressure region into the seal chamber, the part of lubricant staying in the seal chamber.
 7. The rotary shaft according to claim 6, wherein the lubricating passage includes the supply passage and a communication hole formed in a circumferential surface of the rotary shaft.
 8. The rotary shaft according to claim 7, wherein the communication hole is located near the introducing passage.
 9. A piston type compressor connected to an external refrigerant circuit, the compressor comprising: a housing defining a seal chamber, a cam chamber, a plurality of cylinder bores and a suction pressure region; a rotary shaft rotatably supported by the housing, the rotary shaft including a first lubricating passage that interconnects the suction pressure region and the seal chamber for introducing fluid with lubricant in the suction pressure region into the seal chamber, the part of lubricant staying in the seal chamber; a cam located in the cam chamber, the cam being operatively connected to the rotary shaft; a piston located in each of the cylinder bores, the piston engaging the cam to reciprocate in accordance with rotation of the rotary shaft through the cam; a rotary valve connected to the rotary shaft, the rotary valve including an introducing passage, the rotary shaft including a supply passage that interconnects the introducing passage and the suction pressure region for introducing the fluid into the cylinder bore; and a shaft seal device located in the seal chamber, the shaft seal device being located between the housing and the rotary shaft for preventing the fluid from leaking along a circumferential surface of the rotary shaft from the housing.
 10. The piston type compressor according to claim 9, wherein the supply passage interconnects the cam chamber and the suction pressure region for introducing the fluid into the cam chamber, the introducing passage communicating with the cam chamber for introducing the fluid into the cylinder bore.
 11. The piston type compressor according to claim 9, wherein the first lubricating passage includes the supply passage and a communication hole formed in the circumferential surface of the rotary shaft, the communication hole communicating with the supply passage at a first communication opening.
 12. The piston type compressor according to claim 11, the supply passage communicating with the introducing passage at a second communication opening.
 13. The piston type compressor according to claim 12, wherein the second communication opening is located near the first communication opening.
 14. The piston type compressor according to claim 9, wherein the housing includes a second lubricating passage that interconnects the seal chamber and the cam chamber.
 15. The piston type compressor according to claim 14, wherein the housing includes a cylinder block defining the cylinder bores, the cam chamber being defined in the cylinder block, the second lubricating passage extending through the cylinder block.
 16. The piston type compressor according to claim 14, wherein the housing includes: a housing element defining the seal chamber; and a cylinder block fastened to the housing element by a bolt, the housing element and the cylinder block defining a bolt hole, the bolt being inserted through the bolt hole, the second lubricating passage at least partially including: a clearance formed between a circumferential surface of the bolt and an inner circumferential surface of the bolt hole; and a groove recessed in an end surface of the cylinder block that faces the housing element, the groove communicating with the bolt hole.
 17. The piston type compressor according to claim 14, wherein the housing includes: a housing element defining the seal chamber; and a cylinder block fastened to the housing element by a bolt, the housing element and the cylinder block defining a bolt hole, the bolt being inserted through the bolt hole, wherein the piston type compressor further comprising: a valve port plate interposed between the housing element and the cylinder block, the second lubricating passage at least partially including: a clearance formed between a circumferential surface of the bolt and an inner circumferential surface of the bolt hole; and a groove recessed in the valve port plate, the groove communicating with the bolt hole.
 18. The piston type compressor according to claim 9, wherein the suction pressure region includes a suction chamber that communicates with the external refrigerant circuit.
 19. The piston type compressor according to claim 9, wherein the rotary valve is integrated with the rotary shaft.
 20. The piston type compressor according to claim 9, wherein the piston is a double-headed type.
 21. The piston type compressor according to claim 9, wherein the compressor is a fixed displacement type.
 22. A lubricating structure in a piston type compressor connected to an external refrigerant circuit, comprising: a housing defining a seal chamber, a cam chamber, a plurality of cylinder bores and a suction pressure region; a rotary shaft rotatably supported by the housing, the rotary shaft including a communication passage that interconnects the suction pressure region and the seal chamber; a cam located in the cam chamber, the cam being operatively connected to the rotary shaft; a piston located in each of the cylinder bores, the piston engaging the cam to reciprocate in accordance with rotation of the rotary shaft through the cam; a rotary valve connected to the rotary shaft, the rotary valve including an introducing passage, the rotary shaft including a supply passage that interconnects the introducing passage and the suction pressure region for introducing the fluid into the cylinder bores; a shaft seal device located in the seal chamber, the shaft seal device being located between the housing and the rotary shaft for preventing fluid from leaking along a circumferential surface of the rotary shaft from the housing; and a lubricating passage interconnecting the cam chamber and the seal chamber.
 23. The lubricating structure according to claim 22, wherein the housing includes a cylinder block defining the cylinder bores, the cam chamber being defined in the cylinder block, the lubricating passage extending through the cylinder block.
 24. The lubricating structure according to claim 22, wherein the housing includes: a housing element defining the seal chamber; and a cylinder block fastened to the housing element by a bolt, the housing element and the cylinder block defining a bolt hole, the bolt being inserted through the bolt hole, the lubricating passage at least partially including: a clearance formed between a circumferential surface of the bolt and an inner circumferential surface of the bolt hole; and a groove recessed in an end surface of the cylinder block that faces the housing element, the groove communicating with the bolt hole.
 25. The lubricating structure according to claim 22, wherein the suction pressure region includes a suction chamber that communicates with the external refrigerant circuit.
 26. The lubricating structure according to claim 22, wherein the communication passage includes the supply passage and a communication hole formed in the circumferential surface of the rotary shaft.
 27. The lubricating structure according to claim 22, wherein the rotary valve is integrated with the rotary shaft.
 28. The lubricating structure according to claim 22, wherein the piston is a double-headed type.
 29. The lubricating structure according to claim 22, wherein the compressor is a fixed displacement type.
 30. The lubricating structure according to claim 22, wherein the housing includes: a housing element defining the seal chamber; and a cylinder block fastened to the housing element by a bolt, the housing element and the cylinder block defining a bolt hole, the bolt being inserted through the bolt hole, wherein the lubricating structure further comprising: a valve port plate interposed between the housing element and the cylinder block, the lubricating passage at least partially including: a clearance formed between a circumferential surface of the bolt and an inner circumferential surface of the bolt hole; and a groove recessed in the valve port plate, the groove communicating with the bolt hole. 